1. Field of the Invention
The present invention generally relates to error notification methods and information processing apparatuses, and more particularly to an error notification method for an information processing apparatus that can carry out a mirror operation, and to an information processing apparatus that employs such an error notification method.
2. Description of the Related Art
When an error is generated in an information processing apparatus such as a computer system, a circuit that detects the error notifies the error to a processor such as a CPU within the computer system by use of an interrupt signal corresponding to an error level (or error intensity). A software for carrying out the error process of the processor, that is, an error process handler, judges whether to shut down the computer system or to permit continued operation of the computer system, depending on the error level of the error that is notified by the interrupt signal. Accordingly, the computer system is shut down if the error level is high, and the continued operation of the computer system is permitted if the error level is low. Normally, the specifications of the error process handler are determined by a manufacturer of the processor, and the error process handler has a structure such that the software thereof cannot be modified.
On the other hand, in the case of a computer system that is made up of a plurality of processor systems, the interrupt signal described above is notified to all of the processor systems within the computer system. In addition, in the case of such a computer system, the reliability of the computer system is improved by carrying out a mirror operation with respect to memory systems of the processor systems. The mirror operation is sometimes also referred to as mirroring. In the case of the mirroring, 2 processor systems carry out the same process, and the reliability of the processed result is improved by comparing and checking the processed results of the 2 processor systems.
FIG. 1 is a diagram for explaining an example of a conventional error notification method. The computer system includes a system board 1 that is used in a normal mode, a system board 2 that is used together with the system board 1 in a mirror mode, and a home system board 3 that processes errors detected by the system boards 1 and 2. Each of the system boards 1 and 2 includes one or a plurality of CPUs (not shown) and the like, to form a processor system. Each of the system boards 1 and 2 includes an error display register 5, and OR circuits 6 through 8. The error display register 5 includes register parts corresponding to portions where the error is generated, and each of the register parts stores an error level. It is assumed for the sake of convenience that the error level includes a fatal error level Fat, an uncorrectable error level Un, and a correctable error level Cor. The values of the error levels Fat, Un and Cor satisfy a relationship Fat>Un>Cor. An output of the register part that stores the fatal error level Fat is output via an OR circuit 6 as an error interrupt signal ERR2. An output of the register part that stores the uncorrectable error level Un is output via an OR circuit 7 as an error interrupt signal ERR1. In addition, an output of the register part that stores the correctable error level Cor is output via an OR circuit 8 as an error interrupt signal ERR0. The home system board 3 includes circuits for determining partitions of the computer system, and for notifying the error interrupt signals ERR2, ERR1 and ERR0 to each CPU within the computer system.
The error process handler of each CPU within the computer system shuts down the computer system when an error notification by the error interrupt signal ERR2 or ERR1 is received. In addition, the error process handler of each CPU within the computer system permits continued operation of the computer system when an error notification by the error interrupt signal ERR0 is received, because the correctable error Cor is correctable by ECC and the like.
For example, a Japanese Laid-Open Patent Application No. 2000-276364 proposes a fault restoration operation depending on an address index and/or a fault source index.
In the case of the mirror mode, the system board 2 may be able to avoid the error by the mirroring, even when the error interrupt signal ERR2 or ERR1 having the high error level is output from the system board 1. In other words, the error interrupt signal ERR0 having the low error level may be output or, no error interrupt signal may be output, from the system board 2. However, the error process handler of each CPU within the computer system normally cannot be modified, as described above. For this reason, when the home system board 3 receives the error notification having the high error level from the system board 1, an error notification having the higher error level is made with respect to each CPU, similarly as in the case of the normal mode, even if only the error notification having the low error level or no error notification is received from the system board 2, and there was a problem in that the computer system will be shut down.
It is conceivable to switch, in the mirror mode, the error process handler to an error process handler exclusively for the mirror mode. But this conceivable method is undesirable in that it would be necessary to modify the software design of the CPU.